This invention relates to laboratory x-ray instruments used to analyze the chemical compositions of compounds and elements, and other material, specifically by means of x-ray diffraction or fluorescence.
A well known method of analyzing the physical composition of a chemical compound or element or of a material, including crystalline materials, is by means of obtaining a profile of the material's reflectance or fluorescence under x-rays. Such a profile is produced by obtaining a series of data points, at various angles of reflection, of the intensity by which the material reflects x-rays or fluoresces when illuminated at various angles by an x-ray source.
Prior art instruments for x-ray analysis, for example, a typical Philips-Norelco X-ray Diffractometer, utilize a motor-driven worm gear to rotate a material about a first axis and an arm supporting a detector, both rotated in a coordinated manner through a given arc, periodically stopping to obtain readings of the intensity of the x-ray reflectance or fluorescence at various angles. For this reason, a dial display is provided upon the instrument to indicate the relative angular position of the sample. The instrument, in simplest form, then comprises a motor, some form of mechanical input to allow prepositioning of the sample; and a clutch assembly connecting the motor drive to a worm gear driven, indexed sample holding axis and detector positioning means.
Prior attempts have been made to automate such a device in order to eliminate the manual steps of setting the sample at various angles, manually reading the angle off the index scale, and recording x-ray intensity.
A typical method, for instance, as shown in International Business Machines (IBM) Corporation's X-ray Polycrystalline Diffraction II Program Description and Operations Manual, SBa30-1956-0 (undated), is to disassemble the diffraction instrument, gaining access to the clutch mechanism internal to the instrument. The clutch mechanism is then either removed or drilled so as to be pinned to prevent clutch slippage, rendering the clutch permanently inoperable. A computer driven motor or incrementally controlled motor is permanently mounted for driving through the fixed clutch. This technique usually requires the custom design of a motor housing in order to hold the motor and the clutch mechanism in alignment. It may be necessary to spring-mount the motor so as to prevent binding between the shafts, even though there is a consequent loss of precision of angular motion of the motor.
Once made, such modification renders the instrument unusable for further manual operation, and further so affects the entire instrument that it must be reassembled and realigned with the x-ray tube. This is a mechanical realignment that can only be performed by a highly trained, experienced analytical x-ray instrument technician and it results in significant downtime whenever an instrument is so configured.